The invention relates to a welding additive for electric arc welding and laser beam welding of mixed joins made of austenitic and ferritic steel.
In the following, the term electric arc welding includes all benefits which a welding additive is used for producing welding joints as for example metal protective gas welding (MSG), tungsten inert gas and plasma gas welding, as well as hybrid welding methods, a combination of metal protective gas welding and laser beam welding.
In the following, austenitic steel relates in particular to a high manganese steel with up to 30% weight percent manganese, as it is for example known from DE 102 59 230 A1, DE 199 00 199 A1 or DE 10 2004 061 284 A1.
Beside iron and manganese as main elements these steels contain carbon and other elements such as for example aluminum and silicone. The flat products produced from these steels have a high-strength and a high uniform elongation.
Due to their advantageous properties steels with high manganese contents are suitable for construction of transport vehicles, in particular for automobile construction and here in particular for vehicle-body and chassis components. However, other areas use such as for example machine construction or construction are also conceivable.
Oftentimes welding joints between the high-manganese-content austenitic steel and a ferritic steel have to be produced by means of electric arc welding and/or laser beam welding for so-called tailor welded blanks with which crash and weight optimized components can be produced.
While the electric arc welding of same-type high-manganese-content steels is for example known from DE 10 2009 007470 A1 and represents state-of-the-art, for electric arc welding or laser beam welding on mixed joints only additives based on CrNi from the classical black/white-mixed joints, i.e., joints from austenitic Cr—Ni Steels and ferritic steels are known to date.
It is a disadvantage that chromium leads to chromium carbides in the welding zone, so that carbon is no longer available in sufficient amounts as alloy element to form austenite in the high-manganese-content steels. The element Nickel generally leads to the fact that the weld metal has a high tenacity but an insufficient strength.
Because the properties of the welding joint with the known additives on CrNi basis are not compatible with the properties of the used basic materials, the welding additive according to the invention omits these two elements.
Further, coarse, adjacently arranged austenitic and martensitic microstructure phases form during welding of the above mentioned mixed joints which microstructure phases in such a constellation have insufficient mechanical characteristic values. In order to improve the mechanical properties it is a further goal to adjust the alloy composition of the welding additive so that these two phases, which in this case always form, are present in a fine grained and finely distributed manner.